program SquareTriangle;

{$APPTYPE CONSOLE}
var
x1, y1, x2, y2, x3, y3 : real;
s : real;
begin
  readln(x1, y1);
  readln(x2, y2);
  readln(x3, y3);
  s := ((x1-x3)*(y2-y3)-(x2-x3)*(y1-y3))*0.5;
  s := abs(s);
  writeln(s:0:3);
  readln;
end.
 